1. Field of the Invention
This invention relates to an automobile seat occupant sensor and airbag control for detecting the location and weight of a person in car seat, and in particular to a sensor that can detect the presence and location of an occupant using strain sensitive resistors and provide an electrical signal to control activation of an airbag.
2. Description of the Related Art
Various devices are well known for their ability to measure force, pressure, acceleration, temperature, position, etc. by using a sensing structure combined with signal processing electronics. One general type of sensor or transducer for such applications is a resistive strain gauge sensor in which force or pressure is sensed or measured based on strain placed on the resistors. Resistive strain gauges function by generating changes in resistance proportional to force which causes dimensional changes of the resistor.
Many types of strain gauge sensors have been designed and made commercially available. Various strain gauge sensors have proven to be generally satisfactory. Prior art sensors; however, have tended to be rather expensive and not suitable in certain applications such as sensing the presence of an occupant in an automobile seat. A sensor suitable for such an application must be compact, robust, impervious to shock and vibration and yet inexpensive.
Automobile seats can use sensors to activate air bags, which would be deployed during an accident. Injury to infants or small children from air bag deployment with excessive force is a current industry problem. A weight sensor in the seat can be used to control the deployment force during air bag activation. If a heavy person is in the seat, the airbag is deployed at full force. If a light person is in the seat, such as a child, the airbag is deployed at a slower, less forceful rate.
Another problem with airbag deployment is determining the position and posture of a person in a vehicle seat. If the seat occupant is located in the front of the seat, it is desired to activate the air bag with less force. If the seat occupant is located in the rear of the seat, it is desired to activate the air bag with more force. Similarly, if the seat back is an automobile seat is reclined, it may be desired to control the activation of the airbag based upon the seat back angle. For example, if the seat back is reclined fully, it may be desired to activate the air bag with more force. If the seat back is in an upright position, it may be desired to activate the airbag with less force.
U.S. Pat. No. 5,573,269 discloses a system that uses multiple sensors. Several weight sensors are placed in the seat, the floor and a seat angle sensor is attached to the seat back. This system has many disadvantages. It is expensive to produce and install all the sensors. The weight sensor in the seat is attached to the springs which can give inaccurate readings of weight depending on the placement of the sensors in the seat.
Other seat occupant detection systems have been devised based upon ultrasonic sensing technologies. The occupants distance from the dashboard is measured by a sensor. Other sensors try to measure the size of the occupant. Unfortunately, the ultrasonic systems produce frequent errors in calculating the size of the occupant as they have difficulty in interpreting an occupant shifting in the seat, moving the seat forward or backward and reclining the seat.
A current unmet need exists for a reliable, low cost, simple and robust automobile seat weight sensor and system that is used to control airbag deployment. A current unmet need also exists for an air bag control system that can monitor occupant weight, seat position and seat back angle with a minimum number of sensors at a low cost.
3. Related Art
Examples of patents that are related to the present invention are as follows, and each patent is herein incorporated by reference for the supporting teachings:
U.S. Pat. No. 5,573,269 is a apparatus for sensing and restraining an occupant of a vehicle seat.
U.S. Pat. No. 4,556,598 is a porcelain tape for producing porcelainized metal substrates.
U.S. Pat. No. 5,232,243 is an occupant sensing apparatus.
U.S. Pat. No. 5,276,432 is a patient exit detection mechanism for hospital bed.
U.S. Pat. No. 5,739,757 is an vehicle passenger weight sensor.
The foregoing patents reflect the state of the art of which the applicant is aware and are tendered with the view toward discharging the applicant""s acknowledged duty of candor in disclosing information which may be pertinent in the examination of this application. It is respectfully stipulated, however, that none of these patents teach or render obvious, singly or when considered in combination, the applicant""s claimed invention.
It is a feature of the invention to provide a reliable and cost-effective automobile seat occupant sensor and airbag control system for detecting the location and weight of a person in car seat, and in particular to a sensor that can detect the presence and location of an occupant using strain sensitive resistors and provide an electrical signal to control activation of an airbag.
An additional feature of the invention is to provide a vehicle airbag control system for sensing the weight and position of an occupant in a vehicle seat and controlling an airbag, the system includes an airbag and an airbag deployment means for deploying the airbag. Several sensors are fixedly located in a weight path of the vehicle seat. The sensors are located between a seat bottom and a vehicle floor. The sensors are located substantially near an outer perimeter of the seat, each sensor provides an electrical output signal representative of the weight applied by the vehicle occupant at the sensor location. A controller means is connected between the airbag deployment means and the sensors for controlling deployment of the airbag in response to the electrical output signals. The controller means calculates a center of gravity of the seat occupant to locate the position of the occupant in the seat and determines if the occupant is in a first position where the airbag is allowed to deploy or is in a second position where the airbag is prevented from deploying.
Another feature of the invention is to provide a control system for controlling an airbag. The control system controls the airbag in relation to the weight and position of a seat occupant. The system includes an airbag and an airbag inflation means that are connected to the air bag to inflate the airbag. A sensor means is attached to a seat, for sensing a weight of the seat occupant at a sensor location. A processor is connected to the sensors and to the airbag inflation means. A software means operates on the processor to calculate the weight of the seat occupant and determine if the weight of the seat occupant is less than a first magnitude. The software means also prevents actuation of the airbag inflation means, if the weight of the seat occupant is less than a first magnitude and allows actuation of the airbag inflation means, if the weight of the seat occupant is greater than the first magnitude. The software means further can calculate a center of gravity of the seat occupant and determine if the center of gravity is inside or outside a first area. This information is used to prevent actuation of the airbag inflation means, if the center of gravity is outside the first area; and allow actuation of the airbag inflation means, if the center of gravity is inside the first area. The software means can further be used to calculate a seat inclination angle of the seat. This information is used to determine if the seat inclination angle is greater than or less than a first magnitude. The airbag inflation means is prevented from actuating, if the seat inclination angle is less than the first magnitude and allowed to actuate if the seat angle is greater than the first magnitude.
The invention resides not in any one of these features per se, but rather in the particular combination of all of them herein disclosed and claimed and it is distinguished from the prior art in this particular combination of all of its structures for the functions specified. Other features of the present invention will become more clear from the following detailed description of the invention, taken in conjunction with the accompanying drawings and claims, or may be learned by the practice of the invention.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. Those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.